1. Field of the Invention
The present invention relates to a cutting device used in a lateral sealing process, etc. in a filling and packaging apparatus for manufacturing package containers each having a rectangular shape, etc. in cross section and filled with fluid such as juice, etc. and particularly to a cutting device provided with a hydraulic cylinder.
2. Prior Art
There is known a conventional filling and packaging apparatus comprising a rewinder for supporting a web serving as a packing material (hereinafter referred to simply as packaging material web) in a rolled state, a winding apparatus for winding the web in order from the rewinder, a tube-forming apparatus for forming the wound web in a tubular shape after sterilizing it, a fluid supply pipe for filling fluid in the packaging material web which was formed in the tubular shape, and a container-forming apparatus for laterally sealing the web and cutting sealed parts of the web to continuously form pillow-like containers each having a rectangular shape in cross section while downwardly supplying the tube filled with the fluid by the length corresponding to one container, and a container shaping apparatus for bending each end part of the pillow-like containers which are separated into individual ones to shape each pillow-like container in a parallelepiped container to be finally obtained (as disclosed in JP-B 1-23366 and JP-A 58-193206)).
The container-forming apparatus sandwiches the tube filled with the fluid by lengths each corresponding to one container for laterally sealing it, and cuts the sealed parts (intermediate parts between the sealed areas) wherein a press is provided for producing sealing pressure between a pair of lateral seal bars and two pairs of lateral seal bars movable vertically alternately, and wherein a pair of lateral seal bars comprise a heating mechanism called as inductors and a heating bar provided between the inductors and having a portion for receiving a cutter, and a cutting bar which extends laterally from the center thereof and provided with a flat cutter which advances and retreats (see FIG. 2). As a conventional cutting device as the cutting bar, it is known that the advance of the cutter is made by oil pressure, and a retreat of the cutter is made by a spring. Such a conventional cutting device will be now described more in detail.
A cutter retreat cylinder is disposed at the central back side of the cutter, and the cylinder has a piston integrated with a piston rod mounted on the central rear end part of the cutter, and a spring which is coaxially provided with the piston for always giving a biasing force (about 35 Kgf) in a direction of retreating the cutter so that the piston rod is positioned in a retreating position. There are two cutter advance hydraulic cylinders provided at the right and left sides of the cutter retreat cylinder and disposed at both rear end portions of the cutter, and pistons provided in the hydraulic cylinders and having piston rods integrated with the hydraulic cylinders capable of pressing right and left back end parts of the cutter, oil pressure chambers respectively communicating with oil-supply pipes, wherein when the tubular packaging material is cut, oil is supplied from the oil-supply pipes to the oil pressure chambers to advance the piston rods with a force which is greater than a biasing force of the spring, thereby pressing the cutter to cut the lateral sealed parts of the tubular packaging material web. After the tubular packaging material web is cut, the supply of oil from the oil-supply pipes is stopped so that no oil under pressure is supplied to the oil pressure chambers, and hence the cutter is retreated owing to the biasing force of the spring so as to be accommodated into the cutting bars.
In such a lateral sealing apparatus having a complex construction, the spring is excellent as a means for retreating the piston to which a cutter is attached in view of space and cost thereof, and in actual circumstances there has been no problem for practically using the spring so far. The spring employed by this lateral sealing apparatus shows a durability as it is designed, and it is enough to replace the spring with a new one once every couple of months.
The above-mentioned conventional press comprises a stationary engaging member having an upward engaging recess and a movable engaging member having a downward engaging projection engaging with the engaging recess of the stationary engaging member, wherein the engaging members are respectively provided at right and left sides of each seal bar. The movable engaging member is attached to the piston rods of the hydraulic cylinder, and the piston rod is retreated in a state where the movable engaging member pivotally moves to engage with the stationary engaging member so that a sufficient sealing pressure of about 700 Kgf is produced between the seal bars.
The production of sealing pressure in the press owing to the retreat of the piston rod to which the movable engaging member is attached is performed by the oil under pressure of the hydraulic cylinder provided in the press, while the release of the sealing pressure and the advance of the piston rod is performed by the biasing force (about 30 Kgf) of a plurality of springs which are disposed coaxially in the cylinder and have different diameters at the same time when the oil pressure is released (e.g., see FIG. 12 of JP-B 1-23366).
An idea to employ a biasing force other than the biasing force of the spring as a means for advancing the piston rod to which the movable engaging member is attached has not been hitherto considered in view of a space and cost of the lateral sealing apparatus having such a complex construction, and a need for such sealing apparatus has not been demanded so far. The spring provided in the hydraulic cylinder shows durability as designed, and is sufficient to be replaced with another every couple of months.
In a conventional method of retreating the cutter owing to the biasing force of the spring, the cutter cannot be retreated after cutting the tubular-shaped packaging material web when the spring is broken, so that the tip end of the cutter to be accommodated in the cutting bars always protrude from the cutting bars, causing a possibility that a non-sealed part of the web is damaged inadvertently.
When the spring is broken, the cutter cannot be retreated after cutting the web, and the tip end of the cutter to be accommodated in the cutting bars always protrudes from the cutting bars so that energy generated in the inductor of the heating bars is taken away by the cutter, whereby an aluminum foil layer of the packaging material web is insufficiently heated to insufficiently melt a resin layer so as to make the lateral sealing incomplete.
As a result, a package container in which the web is broken or a package container in which incomplete lateral sealing is performed is manufactured, which causes a problem that a filler such as juice, etc. is leaked or leached out from the package container. If such leaking or leaching out of the filler such as juice, etc. from the package container is visually recognized, it can be checked in a manufacturing process, but if such leaking is too small to be visually recognized, it is very troublesome. The reason is that in distribution channels of the germ-free filling and package container, such leaking and leaching out of juice, etc. from the sealed parts causes a serious problem of propagating the mold, etc. and contamination by a microorganism. In a state where the tip end of the cutter to be accommodated in the cutting bars always protrudes from the cutting bars, the unsealed part of the web is inadvertently damaged or the cutter contacts the filler such as juice, etc. so that the filler such as juice, etc. in the package container is contaminated in the microorganic point of view, and then the lateral sealing is performed at the damaged part. As a result, although the external appearance of the package container is normal, there is a likelihood of occurrence of fatal matter such as propagation of a harmful microorganism in the package container for the germ-free filling and package container.
Since the spring is provided in the cylinder, the damaging state of the spring cannot be seen from the outside. Even if the spring is damaged during the manufacture of the package container, the manufacture of the package container continues while the spring is damaged, and hence the damage of the spring is found out when the apparatus are checked upon completion of a day's manufacture so that all package containers manufactured at the same date must be scrapped. To avoid such a situation, it is necessary to replace a spring with another earlier than that designed date, which incurs a troublesome labor to regularly replace the spring and also the increase of running cost involved in the replacement of the spring.